The 5th generation New Radio (5G NR) wireless communication network is the proposed next generation wireless communication network for which telecommunications standards our currently being developed. The 5G NR network will be an end-to-end ecosystem to enable a fully mobile and connected society. The Next Generation Mobile Networks Alliance estimates that 5G NR networks will be rolled out by 2020 to meet business and consumer demands. In addition to providing faster speeds, it is predicted that 5G NR networks also will need to meet new use cases, such as the Internet of Things (internet connected devices), as well as broadcast-like services and lifeline communication in times of natural disaster. Carriers, chipmakers, original equipment manufacturers (OEMS) and out-sourced assembly and test companies (OSATs), have been preparing for this next-generation (5G) wireless standard, as mobile systems and base stations will require new and faster application processors, basebands and RF devices. Although updated standards that define capabilities beyond those defined in the current 4G standards are under consideration, those new capabilities have been grouped under the current ITU-T 4G standards.
In the current standards, the reference signal (RS) is typically generated in the base station (BS) and then transmitted to a User Equipment (UE) device to perform channel estimation. The RS is then used by a receiving UE device to perform channel estimation measurements such as reference signal received power (RSRP) measurements. Thereafter, the UE device generates a report containing the measurement results, which is then transmitted back to the BS. Upon receiving the report, the BS can decide whether to use the particular channel used to transmit the RS for further data communications with the UE device. In a multiple-in-multiple-out (MIMO) system implementing beam forming techniques, wherein multiple directional beams may be used to communicate with a UE device, the BS can use such channel estimation techniques to identify the best beam(s) for communicating with a particular UE device. The RS is also used by a receiving UE device to perform channel estimation measurements such as precoding matrix indicator (PMI) measurements. Thereafter, the UE device generates a report containing the measurement results, which is then transmitted back to the BS. Upon receiving the report, the BS can decide the specific precoding matrix for further data communications with the UE device.
In the 5G NR network, however, it is contemplated that the area coverage of each BS will be smaller than the coverage area of a BS in LTE and as a result the number of BS's in a given area will become larger when compared to current LTE networks. Additionally, it is contemplated that the subcarrier spacing (SCS) in 5G NR networks will increase (e.g., multiple SCS's in the range from 15 KHz to 480 KHz may be supported). This contemplated increase in number of BS's and SCS in 5G NR systems will pose potential problems for generating reference signals for channel estimation, as discussed further below.
A reference signal is generated from a reference signal sequence, which is in turn generated from a pseudo-random number sequence (PRNS) provided by a pseudo-random number generator (PRNG). The PNRG is initialized by an initialization sequence of fixed length L, which is in turn generated by an initialization sequence value (cinit), which is in turn dependent on the value of parameters such BS cell ID numbers and SCS. As the number of BS's in a given area increases, the possible values of BS cell ID's also increases proportionally. Thus, cinit may become too large (e.g., greater than 2{circumflex over ( )}31, which means 2 to the power of 31), resulting in an initialization sequence length that is larger than L, which is too long to be used by the PRNG to generate the PRNS used to generate the RS sequence. Thus, current techniques for generating a reference signal sequence will not be satisfactory for the contemplated 5N NR networks.